Crash sensors have become widely adopted by many of the world's automobile manufacturers to sense that a crash is in progress and initiate the inflation of an air bag or tension of seat belts. These sensors may be electromechanical and constructed from a ball and tube such as disclosed in U.S. Pat. Nos. 5,031,931 and 5,237,134 to Thuen; and U.S. Pat. No. 152,392 to Husby. The ball-in-tube sensor currently in widespread use has a magnetic bias.
In the conventional ball-in-tube sensor, two cantilevered contacts are bridged by the ball and both the ball and the contacts may be gold plated to minimize the contact resistance. If the sensing mass instead of bridging the contacts, provides a varying magnetic field directly related to the sensing mass position to the Magnetic Field Sensor, the gold plating on the ball as well as the contacts themselves can be eliminated.
In U.S. Pat. No. 5,608,270, Meister discloses an impact sensor using a cylindrical permanent magnet axially slidable within a cavity and a magnetic sensing means adjacent the cavity. In the Meister sensor the vehicle impact forces cause the magnet to slide toward the opposite end and the magnetic sensing means provides an electrical impact signal that varies in magnitude as a function of the axial position of the magnet within the cavity. The Meister patent does not disclose a gas damped ball-in-tube sensor using a ferromagnetic sensing means.